About six months ago, on December 11, the Food and Drug Administration authorized the first COVID-19 vaccine for emergency use in the United States. What followed was a push to get that shot, developed by Pfizer and BioNTech, for those at high risk (SN: 01/12/20). Moderna’s jab didn’t lag behind, securing emergency use authorization just one week after Pfizer (SN: 17/12/20; SN: 12/11/20). And then, in February 2021, there were three COVID-19 vaccines when the FDA authorized the firing of Johnson & Johnson (SN: 27/02/21).
Now, about 40 percent of the American population is completely vaccinated. Just over half of the residents received at least one dose. Meanwhile, cases of COVID-19 in the United States and deaths have dropped to their lowest levels since March 2020.
In the midst of continued efforts to vaccinate people, two big questions are planned: Will immune protection against coronavirus be long? Or will people soon need booster shots?
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Right now, “no one knows” if reinforcements will be needed, says Kirsten Lyke, a vaccinologist at the University of Maryland School of Medicine in Baltimore. But researchers are working to find out.
This is what we know so far about coronavirus immunity and possible booster shots.
Immunity lasts at least six months and possibly much longer.
Whether people need COVID-19 booster shots or not depends largely on how long the body’s immune response protects against seriously ill. So far, this protection lasts at least six months and possibly much longer, the researchers say.
Much of what scientists know right now about long-term immunity comes from what they have gathered from people infected with the coronavirus. And it seems that the memory immune to the virus largely follows the rules, at least for most people, says Ali Ellebedy, an immunologist at the University of Washington School of Medicine in St. Louis.
This means that after the virus is imposed, the body unleashes a wave of immune proteins called antibodies and immune cells called T cells to fight the virus. Antibodies typically attack the virus itself while T cells raise alarms or kill infected cells. Together, antibodies and T cells defeat the virus and then help the immune system form memory for the pathogen, Ellebedy says. That immune memory is crucial for protection if a person is exposed to the virus again.
Studies find evidence that most people develop coronavirus immune memory. Ellebedy found signs of antibody memory, for example, in people who have recovered from an infection. People who had mild COVID-19 had antibody-producing immune cells in the bone marrow 11 months after infection, he and colleagues reported on May 24 in Nature. These cells continue to produce antibodies to the virus long after they leave the body, providing protection if a person becomes exposed again.
Evidence is building that vaccines offer similar, if not better, protection. In that case, the drivers may not be needed for some time. In the latest update from vaccine developers, “things looked pretty good,” Lyke says. People who received the Moderna shot still have high levels of antibodies six months after receiving the second dose, researchers reported in April. And the Pfizer jab is 91.3 percent effective against COVID-19 symptoms after six months, the pharmaceutical company announced on April 1 in a press release.
Still, “we don’t know how any of these COVID-19 vaccines worked last year,” Lyke says. The first trials that tested whether vaccines elicit an immune response are now reaching that point and researchers are following participants (SN: 21/07/20).
Coronavirus variants could make booster shots more likely.
Although the protection provided by the immune system is long-lasting, viruses such as coronavirus are adept at circumventing those responses. Case in point: the emergence of viral variants that may make COVID-19 vaccines less effective than those against the original version of the virus (SN: 5/11/21).
“I don’t think we would be talking about potentially empowering” if it weren’t for the variants, Ellebedy says. "What we're seeing so far is that the vaccine is really robust, so why would we even need a booster if the virus doesn't change?"
Available vaccines still protect people against the worst of COVID-19, even if they are infected with any of the circulating variants. But that may not always be the case. “There may be a future variant that we don’t know can come and surprise us,” Lyke says. Still, several COVID-19 vaccines are of flexible design and can be easily adapted to address new variants (SN: 27/01/21). So, it becomes a matter of making the doses.
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Some companies, including Pfizer and Moderna, are already testing booster shots to combat emerging variants, in particular the beta variant that first emerged in South Africa. Moderna's first results suggest that people who received a booster shot using the beta variant version of a viral protein had antibodies that improved the chance of the variant infecting cells compared to people who received a third dose of the original vaccine. .
Still, one question is how it could be the best booster variant, says Jerome Kim, a vaccinologist and director general of the International Vaccine Institute in Seoul, South Korea. Researchers around the world thoroughly monitor circulating flu strains, for example, to find out which strain or strains should be included in flu vaccines. In the future, experts may have to watch out for coronavirus in a similar way.
Low vaccination rates around the world can also make booster cows more likely.
When countries like the United States begin to emerge from the worst of the pandemic, there are many others who are left behind in vaccinations (SN: 26/02/21). This is in part because rich countries have bought most of the doses available to vaccinate their populations, leaving lower-income countries struggling to receive shots.
To date, more than 2 billion doses have turned it into weapons worldwide. Some countries, including Canada, the United Kingdom, Chile, and Israel, have given at least one dose to about 60 percent of their populations. But only 1 percent of people in places like Nigeria and Sierra Leone have received at least one dose of vaccine.
Low vaccination rates in many places pose a problem for efforts to stifle transmission and end the pandemic. And the more the coronavirus spreads, the more opportunities there will be for new variants to appear, increasing the likelihood of booster shots. The coronavirus “managed to find the gaps, like any virus,” Kim says. "It's in the nature of viruses to find weaknesses. And before you know it, there's another mutant."
Some countries are flying blind due to lack of genetic surveillance. Strengthening that capacity in regions such as Africa, Latin America, and South Asia would help control coronavirus diversity in those places and capture emerging variants before it becomes a global problem.
It is also important to take vaccines to places that need them through efforts such as COVAX, an international initiative to help distribute COVID-19 to low-income countries. “We have to start going to places that have very bad outbreaks because we know mutants will be generated,” Kim says.
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“Combined” COVID reinforcers can offer even more protection.
To prepare for a future in which people need COVID-19 enhancements, the U.S. National Institute of Allergy and Infectious Diseases launched a clinical trial on June 1 to test the COVID-19 blend and vaccines.
The big question is whether mix-and-match vaccines boost the immune response against the coronavirus, says Lyke, one of the researchers leading the trial. If someone gets an mRNA vaccine, like Modern or Pfizer, and then gets a Johnson & Johnson boost, "can we increase (the immune response) by changing the platform?" Lyke says.
Mixing different types of Ebola or HIV vaccines, for example, can trigger stronger immune responses than receiving multiple doses of the same vaccine (SN: 6/4/21). The idea is that each shot will activate various parts of the immune system, Lyke says. An mRNA vaccine can cause the body to produce many antibodies that attack the virus. After all, a dose of vaccine like Johnson & Johnson’s (which uses a common cold virus modified so it can’t cause disease) can cause more T cells. ”If you combine (the shots), we hope to show that you get the better of the two. answers that work synergistically, ”Lyke says.
The first results of a similar test conducted in the UK suggest that the response to COVID-19 shots is yes. People who received the COVID-19 shot from AstraZeneca followed by a dose of Pfizer eight weeks later developed potent immune responses, the researchers reported in a preliminary study published June 1 on medRxiv.org. Antibodies from people who received the two different vaccines were better at recognizing variants such as beta compared to those from people who received two doses of Pfizer vaccine.
A separate study in Spain also found that people who received a dose of COVID-19 shot of AstraZeneca followed by a dose of Pfizer had high antibody levels compared to people who received only one dose of AstraZeneca vaccine, the researchers reported in May . But it’s unclear how those levels compare to people who received two doses of the same shot.
One of the benefits of the American test is that it has a flexible design, says Lyke. This means that if new variants emerge, researchers can add new groups to the trial to test newly developed enhancers. "As we get data (on variants) that comes from other countries, we can really start to perfect ourselves in the holes of our data and to which we need to respond."